Copper alloy



Patented Aug. 20, 1940 PATENT OFFICE corrna ALLOY Louis L. Stott, Reading, Pa., assignor to The Beryllium Corporation, New York, N. Y., a corporation of Delaware No Drawing.

6 Claims.

This invention relates to alloys and especially to an alloy of which copper is the primary ingredient, having added thereto certain quantities of silver, cobalt, and beryllium, as more fully pointed out hereinafter.

One of the primary objects of the invention is the provision of an alloy having high electrical conductivity and hardness. Usually the electrical conductivity of an alloy diminishes asthe hardness increases, but the alloy of the present invention is especially useful because of its combined high hardness and electrical conductivity.

The alloy of the invention is particularly suitable for parts of electrical equipment, such as current carrying and contact members, where high strength or good wear resistance combined with high conductivity are required. For example, the improved alloy of this invention is especially suitable for welding electrodes, such 20 as resistance welding electrodes, for all pressure exerting electrodes, for switch fingers, relay contacts, slip rings, commutator segments, etc. The alloy is also of use in special current carrying wires where a combination of high strength, resistance to fatigue and high conductivity is desired.

In addition to the above, it is to be understood that the alloy has still other uses such as in structural parts of switch gear and the like, particularly where these parts are required to carry current and at the same time must have high strength.

Heretofore a number of different alloys have been proposed and used for purposes such as, the above, but diificulties have been encountered for various reasons. In some instances, whereberyllium containing alloys have been employed for welding electrodes, a highly refractory film of beryllium oxide has built up on the electrode to such an extent that overheating and sticking occurred.

With some other alloys proposed heretofore, the electrical conductivity was insufllcient and with still others the strength or hardness was inadequate.

I have discovered that the addition of silver, cobalt and beryllium to copper, in the approximate ranges specified hereinafter, provides a most unusual combination of high hardness and strength andhigh electrical conductivity.

Per cent Beryllium .l.. .2 to .5 Silver .5 to 2.0 Cobalt .5 to 3.0

Copper 98.8 to 94.5

Application January 4, 1938, Serial No. 183,285

The best results appear when operating within the following ranges:

Per cent Beryllium .25 to .45 Silver .80 to 1.40 5 Cobalt 1.00 to 2.00 Copper 97.95 to 96.15

My preferred composition is an alloy containing approximately the following:

10 Per cent 3 Beryllium Silver 1.0 Cobalt a 1.5 Copper 97.2 15

ticularly the combined high electrical conductiv-. g5

ity and high hardness and strength.

The alloy may be heat treated substantially in accordance with the Masing and Dahl United States Patent No. 1,975,113. It may be noted, however, that the presence of the cobalt lowers 30 the solubility of beryllium in, the alpha phase, thus raising the necessary quenching and precipitation temperatures and enabling hardening of the alloy with less, beryllium.

In general, the heat treatment steps include 5 quenching from a. temperature in the region of maximum solubility in copper of beryllium (or a beryllium compound) which is safely below the lowest melting point, and then reheating for a suitable time at a lower temperature to cause hardening by precipitation. I have found 1550 F. to be a suitable quenching temperature when employing ingredients in the ranges specified above, and 900 F. is a suitable precipitation hardening temperature. 5

Desirable properties of my improved alloy apparently flow from precipitation hardening and the property of beryllium and certain beryllium compounds to impart this characteristic to copper alloys. The hardening treatment may be given either before or after cold work, depending on the characteristics desired; in fact my alloy shows a unique capacity to stand severe cold reductions after precipitation hardening.

When heat treated in accordance with the forei going, cold drawn bars of the alloy of preferred composition as specified above (.3% beryllium;

1% silver, 1.5% cobalt, and 97.2% of copper) have a maximum hardness of 90-92 Rockwell B and show an electrical conductivity of about of that of copper. Heat treated castings and forgings also show an excellent combinationof hardness with high electrical conductivity.

The hardness on the Rockwell B scale referred to above was obtained by using a diameter steel ball with a 100 kilogram load.

I claim:

1. A pressure exerting electrode comprising an alloy containing, by weight, from 96.85% to 98.2% copper, from 0.5% to 1.0% silver, from 1.0% to 1.75% cobalt and from 0.3% to 0.4% beryllium.

2. A pressure exerting electrode comprising an alloy containing, by weight, about 97.2% copper, about 1.0% silver, about 1.5% cobalt and about 0.3% beryllium.

3. A resistance welding electrode comprising an alloy containing from 0.5% to 1.0% silver, from 1.0% to 1.75% cobalt, from 0.3% to 0.4% beryllium and the remainder copper and having an electrical conductivity of at least 50% that of copper and a Rockwell hardness of at least on the B scale, using a diameter steel ball with a kilogram load.

4. An alloy 0! the following composition:

. Per cent Beryllium .2 to .5 Silver .5 to 2.0 Cobalt .5 to 3.0 Copper 98.8 to 94.5

said alloy being characterized by high electrical conductivity combined with high hardness.

5. An alloy of the following composition:

Per cent Beryllium .25 to .45 Silver .80 to 1.40 Cobalt 1.00 to 2.00 Copper 97.95 to 96.15

said alloy being characterized by high electrical conductivity combined with high hardness. 6. An alloy of the following composition:

Per cent Beryllium about .3 Silver about 1.0 Cobalt about 1.5 Copper ....about 97.2 26

said alloy being characterized byhigh electrical conductivity combined with high hardness.

' LOUIS L. STO'I'I. 

